The number of infection attempts using this malware increased significantly over the past few weeks, the researchers said.

A new piece of information-stealing malware that appeared earlier this year has been rapidly gaining traction during the past few weeks, with hundreds of infection attempts being detected every day by antivirus vendors.

The malware is called Solarbot and its creator first started to advertise it to cybercriminals in May, security researchers from antivirus vendor Avast said Wednesday. The number of infection attempts using this malware increased significantly over the past few weeks, the researchers said.

Researchers from antivirus vendor ESET have also been tracking the same threat. "We have uncovered many details about this bot since it became active at the end of July, with in-the-wild infections starting mid-August," they said. "There have been reports of thousands of infections, many of them in South America."

Both Avast and ESET antivirus products detect the malware under the name Napolar.

Solarbot/Napolar is advertised through a professional-looking and publicly accessible website that lists the malware's features and tracks the development progress in an actively updated changelog. The site also provides a manual for using the malware and information on how to develop plug-ins for it.

According to the ESET researchers, buying the malware's binary file, which can be used to infect computers, costs US$200.

Solarbot is able to launch several types of DDoS (distributed denial-of-service) attacks, can act as a reverse SOCKS5 proxy, steal POP3 and FTP login credentials from many email and FTP clients, and steal information entered by victims into Web forms in Internet Explorer, Mozilla Firefox or Google Chrome.

However, the malware's functionality can be extended through plug-ins. The bot's developers offer a plug-in SDK (software development kit) and also provide some example plug-ins to steal Bitcoin wallets or collect computer information.

According to data received by Avast from installations of its products, infection attempts with Solarbot are detected on several hundred unique computers every day. The malware's distribution seems to be global, but the most-affected countries are Colombia, Venezuela, Peru, Mexico, Argentina, Philippines, Vietnam and Poland.

Researchers from ESET suspect that the malware is spread through compromised Facebook accounts, because some of the samples found so far have names like "Photo_032.JPG_www.facebook.com.exe." The malware can steal Facebook log-in credentials using its form-grabbing feature, so attackers can use those credentials to access Facebook accounts and spread the malware to other people, the researchers said.

Although this bot is similar in functionality to Trojan programs like Zeus or SpyEye that are already widely used, its popularity might grow because it is actively maintained, easy to use and can be extended easily through plug-ins, the ESET researchers said.

Due to its solid malicious performance and reasonable price of $200, this bot could be on the rise in the near future, the Avast researchers warned.